Global Positioning System Reference
In-Depth Information
FIGURE 8.9.
Air traffic control radar aboard the aircraft carrier USS
Ronald Reagan
.
Note the range circles superimposed upon the display.
U.S. Navy photo by Mass
Communication Specialist Seaman Mikesa R. Ponder.
moving airborne platforms to generate terrain maps of increasingly high
resolution. In recent years, new processing algorithms have permitted 3-D
images to be constructed (fig. 8.10).
NAVIGATION RADAR
Radar sets that assist navigation need not be as sophisticated as the ATC or
terrain-mapping radars of figures 8.9 and 8.10. Much simpler, smaller,
more economical radars can e√ectively aid navigation of aircraft or marine
vessels.
17
Navigational radar sets usually operate over a relatively short
range (to the horizon, for a surface vessel) and with limited signal process-
ing yet provide valuable data. Radar works at night and in all weather
conditions (the operating wavelengths of navigational radar units are cho-
sen so that they penetrate through air and precipitation). Modern marine
17. Marine radars are usually S-band. That is, they operate over a short-wave band
(frequencies of 2-4 GHz and wavelengths of 8-15 cm). Some marine radars work at even
smaller wavelengths; the X-band (X for secret—the nomenclature dates back to World War
II) operates at around a 10-GHz frequency and a 3-cm wavelength; these radars are short
range but with improved bearing estimation accuracy.
